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Snowmass2021 Cosmic Frontier White Paper: Ultraheavy particle dark matter

by Daniel Carney, Nirmal Raj, Yang Bai, Joshua Berger, Carlos Blanco, Joseph Bramante, Christopher Cappiello, Maíra Dutra, Reza Ebadi, Kristi Engel, Edward Kolb, J. Patrick Harding, Jason Kumar, Gordan Krnjaic, Rafael F. Lang, Rebecca K. Leane, Benjamin V. Lehmann, Shengchao Li, Andrew J. Long, Gopolang Mohlabeng, Ibles Olcina, Elisa Pueschel, Nicholas L. Rodd, Carsten Rott, Dipan Sengupta, Bibhushan Shakya, Ronald L. Walsworth, Shawn Westerdale

This Submission thread is now published as

Submission summary

Authors (as registered SciPost users): Nirmal Raj
Submission information
Preprint Link:  (pdf)
Date accepted: 2023-10-04
Date submitted: 2023-04-28 06:07
Submitted by: Raj, Nirmal
Submitted to: SciPost Physics Core
Ontological classification
Academic field: Physics
  • Gravitation, Cosmology and Astroparticle Physics
  • High-Energy Physics - Experiment
  • High-Energy Physics - Phenomenology
Approaches: Theoretical, Experimental, Computational, Phenomenological, Observational


We outline the unique opportunities and challenges in the search for "ultraheavy" dark matter candidates with masses between roughly $10~{\rm TeV}$ and the Planck scale $m_{\rm pl} \approx 10^{16}~{\rm TeV}$. This mass range presents a wide and relatively unexplored dark matter parameter space, with a rich space of possible models and cosmic histories. We emphasize that both current detectors and new, targeted search techniques, via both direct and indirect detection, are poised to contribute to searches for ultraheavy particle dark matter in the coming decade. We highlight the need for new developments in this space, including new analyses of current and imminent direct and indirect experiments targeting ultraheavy dark matter and development of new, ultra-sensitive detector technologies like next-generation liquid noble detectors, neutrino experiments, and specialized quantum sensing techniques.

Author comments upon resubmission

This is a resubmission following addressal of the referee's comments.

List of changes

Dear editor,

We thank the referee for their positive appraisal of our white paper
and recommendation to publish. We also appreciate their valuable
comments that we address below.



The detection sections focus on model-independent bounds on heavy dark
matter, which looks decoupled from the production mechanism. Some
discussion is given in the direct detection section but less in the
indirection part. The paper could benefit greatly from more
discussions on detecting ultra-heavy dark matter for several
mechanisms presented in Sec 2.


We agree. The DM decay signatures we had discussed are agnostic to the
exact cosmological production mechanism so long as particle DM (as
opposed to PBHs, etc.) is produced.

Accordingly, we have now added to the introductory paragraph of the
indirect detection section the following text.

"Ultraheavy DM models in this category may be generically produced in
the early universe by a number of mechanisms discussed above,
including freeze-out, freeze-in, gravitational production, and
involving phase transitions."



The signatures of heavy dark matter models could also be detected by
cosmological observations. The authors may consider adding some
discussions on this.


We appreciate the suggestion. To the end of the indirect detection
section we have added the following text.

"Finally, cosmological observations could also constrain ultraheavy
DM. CMB anisotropies would carry imprints of DM scattering with SM
matter, which may be exploited to probe a wide range of DM
Moreover, ultraheavy DM produced gravitationally is accompanied by
primordial non-Gaussianities that may be enhanced and observed in the
CMB power spectrum~\cite{Li:2019ves,Li:2020xwr}."



For gravitational particle production through inflation, the authors
wrote that the production is efficient when dark matter mass is
comparable to the inflationary Hubble scale. But I think the
production is efficient when the mass is much smaller than the Hubble


As we had noted, there may be exceptions, however gravitational
production as in WIMPzilla models is indeed generically most efficient
when the particle mass is comparable to the Hubble scale at the end of
inflation. This is stated, e.g., at the end of page 1 in


With these changes we hope our manuscript will now be taken up for publication.

Published as SciPost Phys. Core 6, 075 (2023)

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